How To Install Flash Drive On Mac. On the left-hand pane select the USB drive not the partition under it if any. The flash drive must be at least 8GB in size in order to fit the macOS installer on it.
Press and hold the Option Alt key immediately after turning on or restarting your Mac. Plug the USB flash drive into your Mac. Run OS X Yosemite on a different drive through the same software.
Launch the Disk Utility to format the USB Flash drive.
Launch the Disk Utility application. Open the installation manager. Click View from the top silver menu bar. Youll want to use the Disk Utility app for this method.
